<?php $categorie = mysql_query("SELECT * FROM categoria")?>

<select name="c" onchange="SearchCrit();" id="cat" class="search_category">
  <?php while($categoria = mysql_fetch_array($categorie, MYSQL_ASSOC)): ?>
  <option value="<?php echo $categoria['id']?>" ><?php echo $categoria['descrizione'] ?></option>
  <?php endwhile;?>
</select>